The radio data system (RDS) has existed since the late 1980s. Over the years, continual improvements have been made in the field of RDS demodulation and RDS decoding in the receiver. The services of the RDS are certain types of data which may be transmitted, and evaluated by the radio receivers according to the type of data. In addition to the widely used functions for program identification, radio traffic service, and alternative frequencies, RDS provides further options for additional information/services. RDS is modulated to 57 kHz, with suppression of the carrier. A digital two-phase shift keying method (2-PSK) is used as the modulation method.
European Patent Application No. EP 0627834 A1 describes a circuit system for a demodulator of a radio data signal in a broadcast receiver.